Ashlands is almost certainly next, based on the early roadmaps and on the presence of a small amount of prep work there thats in the game, and all but guaranteed by the progression of fishing as implemented with Mistlands.
As for Oceans, its hard to do that much with oceans since its a biome you can, by intentional design, access almost from the start of the game. They might be able to add an extra smaller critter or two maybe, assuming they can implement a purpose for whatever they provide (Its one of their design requirements that everything in Valheim has a purpose), but otherwise I would expect fishing stuff and similar to be the main area of expansion for ocean stuff. I'm guessng that Fish 'n Bread is just the first new recipe for the expanded fishing stuff, and that more recipes will (and should) eventually come for the lower tier fish. Otherwise I think they cant do much, critter-wise, with the oceans unless there is an extra limitation on when players can really get to that bit of ocean. Maybe adding a cold-resist requirement for new ocean stuff if you're way up north, or fire resist for way down south, to create ocean areas that are ocean but have a frozen north or ashlands tag attached to them? That would enable them to add more ocean stuff in those areas with no issue of a noob in leather armor and a raft wandering into it.